Photographic silver halide emulsions containing thiol compounds



Unite t s m nf PHOTOGRAPHIC SILVER HALIDE EMUIJSIONS CONTAINING THIOL COMPOUNDS Leslie Alfred Williams, Wealdstone, England, assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Application April 29, 1957 Serial No. 655,472

Claims priority, application Great Britain June 4, 1 956 11 'Claims. (Cl. 96-67) This'inventionrelates to light-sensitive silver halide emulsions and to such emulsions containing fog inhibiting agents, and/or anti-plumming agents.

It is Well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given. This is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation; in this invention, I am not concerned with the latter.

Fog depends bothon the emulsion and the conditions of development; for a given emulsion it increases with the the whole area of the sensitive coating, but when severe,

it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulphide. and other reactive sulphur compounds, hydrogen peroxide, vapour, and strongly reducing materials. While anti-foggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, orduring development to maximum contrast and speed, or both.

Silver halide emulsions, especially those used on paper supports, are often subject, on processing and especially.

on glazing, to. that form of image degradation known as plumming. Compounds which reduce this effect are called anti-plumming agents.

It is, therefore, an object of my invention to provide photographic silver halide emulsions stabilized against the formation of fog. Another object is to provide photographic silver halide emulsions which give rise to prints which can be hot glazed or ferrotyped without objectionable plumming. Still another object is to provide photographic silver halide emulsions having improvedsensitiv ity without objectionable increased in fog when] said emulsions are stored under adverse conditions of temperature and humidity. Other objects will become apparent from a consideration of the following description and examples.

According to the present invention there is provided a light-sensitive silver halide emulsion containing an anti- 2,887,378 Patented May 19, 1959 2 fogging and/or anti-plumming compound having the general formula: l 1

N N Rs-h='1 i wherein X represents ,-CH=CH--, S, O, NH or CR,'=,N--- (R' representing a hydrogen atom or an alkyl groups, such as methyl, carboxymethyl, ethyl, propyl, butyl, etc., especially an alkyl group containing from 1 to 4 carbon atoms),Y,ahd Z represent hydrogen atoms or monovalent substituents such as alkyl groups (e.g., methyl, ethyl, etc.) or hydroxyl groups and may be the same or different, or Y and Z together represent the atoms necessary to complete a benzene ring, and R represents hydrogen or an alkyl group, such as methyl, carboxymethyl, ethyl, propyl, 'butyl, etc., especially an can be made by heating 1-(2-quinoly1)-4-phenylthiosemicarbazide to 156 C. in an oil bath (Marckwald and Meyer, Berichte, 33 (1900), 1888. r

I have found that by this reaction compounds of gen eral formula I wherein X represents S, O, NH or= -CR=N- can conveniently be made. Such compounds can -also be made by the method described in E. B. Knott and L. A. Williams copending application Serial No. 655,512, filed on even date herewith, now U.S.

Patent 2,861,076, issued November 18, 1958. The resulting compounds can, if desired, be alkylated, e'.g., by

means of an alkyl ester such as methyl iodide and alkali such as sodium hydroxide, to give the compounds of the general formula in which R represents an alkyl group.

Representative compounds of the general formula given above which can be used in the present invention arez (1) 2'z3' dihydrobenzothiazolo 2':3T :5::4: triazole- (2) 2": 3' dihydrobenzimidazolo- 2":3':5':4 triazoler 3) 2'13" diliydrobenz'oxazolo 2':3':5 :4 triazolengee ii 6 4- hydroxy 6 methyl 1:2:3a:7 tetraazaindene- 3-thiol.

A solution of the compounds of the invention when added in suitable concentration, before coating, to unsensitized, chemically sensitized, or optically sensitized photographic emulsions may not (depending on concentration) appreciably alfe'ct the sensitometric values for sensitivity and fog when measurements are made soon after coating. When sensitomet'ric measurements are made at appreciable intervals of time,at elevated temperatures' and dry or somewhat humid conditions, these compounds do stabilize photographic speed and maintain [fog at a low' level.

The preparation of silver halide emulsions involves three separate'operations: (11) the emulsification and digestion or ripening of the silver-halide, (2) the freeing ofthe emulsion from excess soluble salts, usually by washing, and (3) the second digestion or after-ripening to obtain increased sensitivity. (Mees The Theory of the Photographic Process (1942).) I prefer to add the fog-inhibiting agents after the final digestion or afterripening, although they can advantageously be added prior todigest-ion.

The photographic emulsions used in practicing my invention are generally of the developing-out type; also, it is to be understood that photographic emulsions of vary ing halide content can advantageously be used. The antifoggant compounds used in my invention have been found particularly useful when employed in conjunction with gelatino-silver-bromiodide emulsions, although they can also be advantageously employed for stabilizing other silver halide emulsions, such as 'gelatino-silver-chloride, bromide, chlorobfomide, chlorobrorn'iodide, etc.

The emulsions can also be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard U.S. Patent 1,574,944 and U.S. Patent 1,623,499, and Sheppard and Bringham U.S. Patent 2,410,689.

The emulsions canalso be' treated with salts of the noble metals such as ruthenium, rhodium, palladium,

iridium and platinum, all of which belong to group VIH of the periodic table of elements and have an atomic Weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller and Dodd U.S. Patent 2,399,083, or stabilized with gold salts as described in Damschroder U.S. Patent 2,597,856 and Y-utzy and Leermakers U.S. Patent 2,597,915. Suitable-compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925), or bis-(fi-aminoethyl) sulfide and its water-soluble salts (Lowe and Jones U.S. Patent 2,521,926).

The emulsions can also be stabilized with the mercury compounds of Allen, Byers and Murray U.S. Patent 2,728,663, Carroll and Murray U.S. Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665.

The compounds of my invention are effective in the presence or absence of optical sensitizing dyes. Since optical sensitizing may affect stability of emulsions with respect to sensitivity, fog and latent image changes, the action of the compounds of this invention is not completely independent of optical sensitizing or other emulsion variables. It has been found, however, that both non-colour-sensitized emulsions and emulsions sensitized with cyanine or merocyanine dyes or both may be treated with compounds of the general formula first given above.

The most useful amount of the compound to employ will depend upon the particular emulsion, but is generally between 0.003 and 2.0 gm. for an amount of wet emulsion containing the equivalent of 127 gms. of silver. At these concentrations, an increase in emulsion speed is obtained forhigh intensity exposure, while the low intensity speed is not impaired to the degree associated with other stabilizers, nor is the speed of the emulsion to safe-lights increased. High intensity exposure means exposure to a light source of colour temp. 5400 K., ex-

posure time 5 sec., max. log exposure 1.42. Low intensity exposure means exposure to a filtered (neutral density) light source of colour temp. 5400 K., exposure time 30 secs, max. log exposure 1.35. These compounds can, in addition, be used in the presence of certain developme'nt accelerators Without impairing the resulting gain in speed. However, too great a quantity in a fast emulsion may cause loss of sensitivity. With fast bromide or bromiodide emulsions the compounds are usually employed as anti-fogging agents and the amount should then preferably lie between 0.003 and 0.1 gm. for an amount of wet emulsion containing the equivalent of 127 gms. of silver. With slower emulsions, more may be used. The compounds are usually employed as antipumping agents with slow emulsions, for example, silver chloride emulsions, and the amount may then be between 0.1 and 5.0 gms. but preferably n'otmore than 2.0 gms. for an'arnount of wet emulsion containing the equivalent of 127 gms. of silver.

The stabilizing action was determined by incubation of the emulsions (silver-bromiodide unless otherwise indicated) for one or two weeks at F. and constant humidity unless otherwise stated in the examples. The resultsof aging tests are tabulated below and compare speed 10/ E), gamma and fog of the emulsions with and without the stabilizing compound.

assasrs 5 Incubations were carried out at 42% RH. (dry tests) or 94% RH. (wet tests). Exposures were made on an intensity scale sensitometer.

Table l EMULSION DATA (HIGH INTENSITY)5 MINUTES DEVELOPMENT IN D190 (OLEYLPOLYETHYLENEOXIDE ETHER, 5 GMS./127 GMS. AG)

Control; 4, 000 .00 1.000 3,320 0. 42 Compound No. 5.--- 0.005 4, 200 .17 2,150 0.35 3, 640 0.30

Table II LOW INTENSITY AND SAFE-LIGHT SPEEDS Speed, Steps above fog Safe-light Fog Speed, 0.2 Fog above fog I 0.2 0.8

Control 11.4 7.7 .13 12.8 .11 Compound N0. 5 11.2 7. 7 .11 12. 12

Table III EMULSION DATA (HIGH INTENSITY EXPOSURES) 6 MINUTESa DEVELOPMENT D191:

1 Initial 3 Days Wet 7 Days Dry Ooncn., Incubation Incubation gms./127 Ag Speed Fog Speed Fog Speed Fog Control (fast bromiodide emulsion) 3, 540 0.11 1,072 0.80 6,000 0.5 Compound No. 1-- 0.01 3,250 0.10 1, 232 0.21 5, 040 0.35 Control (fast bromiodide emulsion) 2,150 0.22 2,000 0.31 Compound N0. 3.- .001 2,200 0.17 1,700 0.23

Table IV Initial (3 min. develop- Concn., Speed ment D190) Emulsion Data guts/127 Step, gms. Ag .1 log unit Fog Gamma Control (high contrast chlorobromide emulsion) 16. 3 0.70 8.0 Compound No. 11.1 0. 30 7.0 0 7.35 0.25 6.3

The data in the following tables V and VI show that the compounds of my invention when added to a silver chloride emulsion give a desirable increase in the contrast of certain grades of emulsions without concomitant tendency to fog formation on prolonged development.

Table V SENSITOMETRIO VALUES Where speed=10 /E and E=exp. necessary to produce deusity of 0.5; 1 =exposing scale; =1og bar 1 6 Table VI ANTI-PLUMMING (MEASURED AS THE MAXIMUM DENSITY ON THE PAPER TESTED) Normal Cold Hot dry glaze glaze 1. 65 1. 70 1. 45 1. 73 1. 76 1. 7G 1. 65 1. 70 1. 45 Compound No. 1-- 1. 68 1. 71 1. 75

In the foregoing Table VI, the headings have the following meanings:

Normal dry means drying in an ordinary room at room temperature.

Cold glaze means glazed on glass in the ordinary way at room temperature. Hot glaze means glazing at 200 F.

Developer Dl9b has the following composition:

on a rotary glazing machine Grams N-methyl-p-aminophenolsulfate v 2.2 Hydroquinone 8.8 Sodium sulfite (anhydrous) 72.0 Sodium carbonate (crystalline) 130.0 Potassium bromide 4.0

Water to make one liter.

In a manner similar to that illustrated above, other compounds selected from those represented by Formula I can be incorporated in photographic emulsions for the purpose of stabilization and/or anti-plumming. The

Instead of adding the fog-inhibiting or anti-plumming agent directly to the photographic emulsion,.it is sometimes desirable to incorporate the same in a separate layer which is placed in contact with the silver halide emulsion layer which is to be treated. Under such conditions, of course, it is advisable to use a higher concentration of fog-inhibiting or'anti-plumming agent than indicated above. The compounds of my invention function advantageously in acid or alkaline photographic silver halide emulsions. In alkaline emulsions, water-soluble salts of the compounds of Formula I above are formed to some extent, although it is to be understood that the salts of the compounds of Formula I can be used di-- rectly in the photographic silver halide emulsions of my invention. Alkali metal salts of the mercapto compounds of Formula I above can be formed simply by contact? ing such mercapto compounds with an aqueous solution of an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide, etc. Other metal salts such as the silver salt, can be prepared by treating an alkali metal salt of said mercapto compounds with silver nitrate. The ammonium salts of the mercapto compounds of Formula I above can be prepared by simply contacting said mercapto compounds with ammonia or an organic amine, such as pyridine, triethylamine, triethanolamine, aniline, etc.

It has also been found that Compound I above can be prepared according to the following method:

Benzthiazolylhydrazine (0.1 mol.) was shaken together with carbon disulphide (0.10 mol.) and potassium hydroxide (0.10 mol.) in an alcohol (75 cc.)-water (75 cc.) mixture. After some time the original crystals had completely dissolved and. a more flocculent solid answers was suspended in the liquid. This mixture was refluxed with ethyl bromide (0.11 mol.) for 4 hours during which time the solid dissolved: The solution was treated with potassium hydroxide (0.2 mol.) and refluxed for 15 hours. After cooling the solution was acidified with hydrochloric acid and the product collected. It was purified by dissolving in sodium carbonate solution, boiling the solution with charcoal, filtering and acidifying the filtrate. The dried precipitate (pale yellow needles) melted at about 243 C.

What I claim as my invention and desire secured by Letters Patent of the United States:

1. A photographic silver halide emulsion containing a compound selected from those represented by the following general formula:

I II -o Z-C i, Its-i: N

wherein X represents a member selected from the class consisting of a vinylene group, a sulfur atom, an oxygen atom, a NH group, and a group, wherein R represents a member selected from the class consisting of a hydrogen atom and an alkyl groupcontaining from 1 to 4 carbon atoms, R represents a member selected from the class consisting of a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms, an alkali metal atom, a silver atom, and an ammonium group, and Y and Z are selected from the class consisting of (l) radicals directly attached only to the adjoining carbon atoms and (2) radicals which together and with the adjoining carbon atoms form a benzene ring, said radicals (1) directly attached only to the adjoining carbon atoms being selected from the class consisting of a hydrogen atom, a hydroxyl group, and an alkyl group containing from 1 to 4 carbon atoms.

2. A photographic silver halide emulsion as defined in claim 1 wherein said emulsion is a photographic gelatino-silver-halide developing-out emulsion.

3. A photographic gelatino-silver-bromiodide developing-out emulsion containing a compound selected from those represented by the following general formula:

Its-o l T wherein X represents a member selected from the group consisting of a vinylene group, a sulfur atom, an oxygen atom, and a NH group, Y and Z together represent the atoms necessary to complete a benzene ring, and R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containingfrom 1 to 4 carbon atoms, an alkali metal atom, a silver atom, and an ammonium group.

4. A photographic gelatino-silver-halide developingout emulsion containing a compound selected from those represented by the following general formula:

wherein. X represents a member selected from the group consisting, of a-vinylene group, a sulfur atom, an oxygen atom, and a" NH group, R represents a member selected i N Hal i 7. A photographic silver halide emulsion containing a compound represented by the following formula:

N N -41 l 8. A photographic silver halide emulsion containing a compound represented by the following formula:

9. A photographic silver halide emulsion containing a compound represented by the following formula:

HSC=N 10. A photographic silver halide emulsion containing a compound represented by the following formula:

11. A photographic element comprising a silver halide emulsion layer and an organic colloid layer, and incorporated in at least one of said layers a compound selected from those represented by the following general wherein X represents a member selected from the class consisting of a vinylene group, a sulfur atom, an oxygen atom, a group, and a group, wherein R represents a member selected from the class consisting of a hydrogen atom and an alkyl group containing from 1 to 4 carbon atoms, R represents a member selected from the class consisting of a hydrogen atom, an alkyl group containing-from l to 4 carbon atoms, an alkali metal atom, a silver atom and an ammonium group, and Y and Z are selected from the class consisting of (1) radicals directly attached only to the adjoining carbon atoms and (2) radicals which together and with the adjoining carbon atoms form a benzene ring, said radicals (1) directly attached only to the adjoining carbon atoms being selected from the class consisting of a hydrogen atom, a hydroxyl group and an alkyl group containing from 1 to 4 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,566,658 Fry Sept. 4, 1951 

1. A PHOATOGRAPHIC SILVER HALIDE EMULSION CONTAINING A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA; 